Interference lithography or holographic lithography is a technique for efficiently fabricating a large-scale micro-nano structure, and the period of the micro-nano structure is determined by the wavelength and included angle of interference beams (the period is proportional to the wavelength and inversely proportional to the sine value of the included angle between the interference beams); the orientation of the micro-nano structure is determined by the wave vector of the interference beams; and the phase distribution of the fringe is determined by the relative phase difference of the interference beams. The interference lithography can be freely combined with other technologies such as vapor deposition, etching and so on, which provides a foundation for the application of micro-nano structures in photonic crystals, biomedicines, microelectronics and other fields.
The interference lithography system is classified into an amplitude-splitting interference system and a wavefront-splitting interference system, and the two systems split an incident light into two or more coherent beams for interference by a light-splitting device, which is usually selected from a half mirror, a prism, a grating, a diffractive mask and a Lloyd's mirror, etc. Regardless of which kind of light splitter, the structural parameters of the micro-nano structure are fixed, and cannot change in real time. Even with a gimbal mirror, the period of the micro-nano structure can only be changed in a limited range, but its corresponding optical setup is complex.
In order to achieve a spatial frequency modulation of the micro-nano structure, U.S. Pat. No. 5,132,812 and the improvement thereof U.S. Pat. No. 5,262,879, U.S. Pat. No. 5,822,092 and U.S. Pat. No. 5,132,812 use an interference of three sets of beams with different included angles to form three grating pixels with different spatial frequencies, realizing discrete modulation of the spatial frequencies of a grating. Chinese patents CN 01134127.0, CN 200510095775.2, CN 200510095776.2, CN 201010238377.2, and CN 201010503788.X disclose a method to achieve discrete modulation of the spatial frequencies by switching light-splitting gratings having different spatial frequencies, with a binary grating as a light-splitting element.
However, at present, for new materials based on the micro-nano structure, such as new color display, true color 3D display and metasurface material, there is a need for the lithography system to fabricate parameters such as period, orientation, duty cycle and even pattern in real time.